Authentic Thai Peanut Sauce

In a blender, combine corn oil, onion, garlic and hot chili pepper; blend for 1 minute. Empty the mixture into a saucepan and place over low heat until the mixture starts releasing aroma. Add peanut butter and mix well over low heat. Add water and let it simmer for 10 minutes or until thickened. Stir in vinegar and sugar; continue to simmer for another 1-2 minutes. Taste and add more vinegar and sugar if the mixture does not have the sour and sweet taste. Place sauce in a shallow plate for satay dipping or pour over fresh salad.